Far-infrared laser oscillation from a very small p-Ge crystal under uniaxial stress

We report on pulse laser oscillation from a p-Ge intervalence band (IVB) laser composed of a Ga-doped Ge crystal measuring about 1×1×5 mm3 which is a very small volume compared with those reported so far for shallow-acceptor-doped Ge. Laser oscillation is only achieved under uniaxial stresses greater than 1300 kg/cm2. We find that the optimum stress for lasing is around 3500–4100 kg/cm2 when the p-Ge IVB lasers are operated at liquid helium temperature. The minimum electric power needed for lasing is only 280 W at a peak period of pulse emission.